1. Field of the Invention
The present invention relates to a motor-assisted power steering apparatus for a vehicle.
2. Description of the Related Art
A recent motor-assisted steering apparatus requires more electric power as it has been adopted to popular cars which have become bigger and heavier.
In such a motor-assisted steering apparatus, because the motor control circuit is disposed on a radially outside portion of the motor, the switching elements in the control circuit are located remote from the brushes of the motor. Thus, the electric resistances of wires connecting the brushes and switching elements are substantial and cause temperature rise of the controller, which in turn causes insufficient performance of the motor and radiation of electric noise.
In order to prevent the temperature rise, it is necessary to control the current flowing in the lead wires by detecting temperatures of the lead wires, switching elements and brushes. This necessitates many temperature sensors and increases the production cost.